[rules-dev] Accessing Drools compiled classes

[Mark Proctor]

I actually want to move away from compile time generated bytecode inside 
of the packages. Instead I want to move to just keeping validated 
Strings that can be executed via MVEL. Additional we would use ASM to 
bytecode compile often used strings at runtime.

So I think giving you direct access to generated bytecode would be a bad 
thing, it's internal and unstable and you can be sure we'll change it as 
we want.

What you want is to ensure that certain types are imported so Drools can 
see them, right? So instead we should be looking at some sort of 
analysis tool to provide this, we sort of have this already, but it 
won't be complete for your purposes but can be extended. So it tells you 
want classes are used and were, and you can use the drl parser to 
extract imports etc.

The resouce type you suggest won't work. The generated class is just for 
the consequence or some aslects of the "when" it is not the entire rule, 
so in itself is not a complete resource. Plus again I'd rather move 
complete away from this pre-compiled concept and more to validated 
strings with on the fly generation.

That said there is a need for environments like app-engine which don't 
allow runtime bytecode generation and people want the perf boost of 
bytecode to have fully pre-compiled rule sets. I would consider 
something like this, where a .jar has all the pre-compiled rules. But we 
are a long way from this, first we need to get an ASM rule compiler 
working, that can compile a complete rule, then we can look into a full 
pre-compiled ruleset.

Mark
On 26/10/2010 08:49, Guillaume Sauthier wrote:
> Thanks for your answer Edson.
>
> The reason I have is that runtime generated stuff usually don't fit well
> in an OSGi model.
>
> When you take a bundle, it has a statically defined set of "imported
> packages". that means that when the bundle has been compiled, a list of
> packages to be wired in at deployment time has been computed. This list
> of packages if inferred from what the .class files (in the bundle)
> requires to be executed (think of them as external dependencies).
>
> Now if we generate some classes at runtime in an OSGi environment, we
> can see that generated classes can have different (or additional)
> requirements in terms of java packages. So usually, with OSGi, that ends
> up by adding a special header called DynamicImport-Package into the
> MANIFEST, with the side effects of breaking modularity :-(
>
> This is what I want to avoid by having access to the generated classes
> at the compilation phase: I can then use this bytecode (IOW giving it to
> Bnd [1]) to complete the Import-Package MANIFEST header with the right
> set of imported java packages.
>
> As a second issue, less important for the moment and more runtime
> oriented this time, I would like to know if/how we can add a new kind of
> Resource.
> Once we have generated the bytecode in the compilation phase, we can
> assume that all the stuff is already here in the bundle. Why can't we
> use it ?
> I've seen the PKG Resource type, but it's some kind of serialization of
> a whole Package, couldn't it be possible to have a new Package type (or
> way to create a Package) that can use the ClassLoader to get access to
> the already present bundle's resources instead of using the byte[] from
> the serialized Package ?
>
> WDYT?
>
> Thanks
> --G
>
> [1]. http://www.aqute.biz/Code/Bnd
>
> Le 25/10/2010 21:26, Edson Tirelli a écrit :
>>      Not exactly sure how helpful would it be to store the generated
>> bytecodes in an osgi bundle. Anyway, there is no API right now to do
>> that, but you can use reflection to achieve the same:
>>
>>           PackageCompilationData data = pkg.getPackageCompilationData();
>>           Field field = PackageCompilationData.class.getDeclaredField( "store" );
>>           field.setAccessible( true );
>>           Map<String, byte[]>   store = (Map<String, byte[]>) field.get( data );
>>
>>      If you can justify the need for such an API, I guess we could be
>> convinced to add one.
>>
>>      Edson
>>
>>
>>
>>
>> 2010/10/25 Guillaume Sauthier<guillaume.sauthier at ow2.org>:
>>
>>> Hi team
>>>
>>> I've tried the IRC (without much success I admit), maybe here someone will
>>> have some thoughts to share :)
>>>
>>> I'm looking for a way to "intercept" the classes being generated by the
>>> drools compiler.
>>> I've seen that the classes bytecode is stored deep in
>>> PackageStore/JavaDialectRuntimeData, so deep that I cannot easily access it
>>> :)
>>> The objective is to be able to give theses classes to Bnd (I want to store
>>> all of that in an OSGi bundle) so that appropriate Import-Packages can be
>>> computed. That will avoid to have DynamicImport-Packages all around my
>>> bundles :)
>>>
>>> Currently, what I get from the drools compiler is a
>>> Collection<KnowledgePackage>   but I have no API (or didn't find any) to
>>> access (or know) the classes generated by the compiler.
>>>
>>> Any ideas ?
>>> Thanks
>>> --Guillaume
>>>
>>> _______________________________________________
>>> rules-dev mailing list
>>> rules-dev at lists.jboss.org
>>> https://lists.jboss.org/mailman/listinfo/rules-dev
>>>
>>>
>>>
>>
>>
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